8.7. Chapter 8 Exercises

1. Fix the 5 syntax errors in the code below to print a countdown of the numbers from 10 to 0.

   counter = 10 while Counter > 0: Print(counter) counter = Counter + 1

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2. The following code will loop infinitely. Make one change that will make it loop only 5 times.

   x = 5 while x > 0: print(x) x = x + 1

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3. Make 5 changes to the code below to correctly print a count up from -10 to 0.

   output = "" x = -10 while x < 0 x = x - 1 output = output + str(x) + " " print(output)

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4. Fix the errors in the code below so that it uses 2 loops to print 8 lines of *.

   for x in range(1,2) y = 0 while y < 4: print("*") y += 1

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5. Finish lines 1 and 5 so that the following code correct prints all the values from -5 to -1.

   output = x = -5 while x < 0: output = output + str(x) + " " x = print(output)

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6. Complete the code on lines 4 and 6 so that it prints the number 6.

   x = 3 i = 0 while i < 3: x = i = i + 1 print()

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7. The code below is supposed to print an estimate of the square root. But, the indention is wrong on 4 lines. Fix it.

   target = 6 guess = 2 guessSquared = guess * guess while abs(target-guessSquared) > 0.01: closer = target / guess guess = (guess + closer) / 2.0 guessSquared = guess * guess print("Square root of", target,"is", guess)

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8. The function currently takes a start and stop argument and uses a for loop to find the sum of all the numbers between them (inclusive). Change the for loop to a while loop while still using the parameters.

   def sumFunc(start, stop): sum = 0 for num in range(start, stop + 1): sum = sum + num return sum print(sumFunc(1,10))

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9. The program below is supposed to print the times tables for 1 to 3, but there are 5 errors. Fix the errors.

   for x in range(1,3): for y in range(1,10) print(str(x) + " * " str(y) + " = " x*y)

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10. Rewrite the code that prints the times tables for 1 to 3 using a while loop and a for loop instead of two for loops.

    for x in range(1,4): for y in range(1,11): print(str(x) + " * " + str(y) + " = " + str(x*y))

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11. Rewrite the following code to use a while loop instead of a for loop.

    product = 1 # Start out with nothing numbers = range(1,11) for number in numbers: product = product * number print(product)

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12. Fix the errors so that the code gets the average of the numbers from 1 to 10.

    sum = 10 x = 0 while x < 11: sum = x x = x + 1 average = sum / 2 print(average)

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13. Rewrite the following code to use a while loop instead of a for loop.

    # STEP 1: INITIALIZE ACCUMULATOR product = 1 # init product to 1 # STEP 2: GET DATA numbers = range(10,21,2) # STEP 3: LOOP THROUGH THE DATA for number in numbers: # STEP 4: ACCUMULATE product = product * number # STEP 5: PROCESS RESULT print(product)

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14. The code below currently enters a loop where it keeps printing “Even”. Fix the code so that it prints “Even” and “Odd” for numbers 0 to 9.

    number = 0 while number < 10: while number % 2 == 0: print("Even") while number % 2 != 0: print("Odd") number += 1

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15. Modify the code below to create a function that will take numbers as input until you enter a negative number and then will return the average of the numbers.

    sum = 0 count = 0 message = "Enter an integer or a negative number to stop" value = input(message) while int(value) > 0: print("You entered " + value) sum = sum + int(value) count = count + 1 value = input(message) print("The sum is: " + str(sum) + " the average is: " + str(sum / count))

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16. Fix and change the code so it prints a table of division instead of multiplication for -10 to -1.

    for x in range(0,11) for y in range(1,11): print(str(x) + " * " + str(y) + " = " + str(x*y))

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17. Create a function to calculate and return the sum of all of the even numbers from 0 to the passed number (inclusive) using a while loop.

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18. Write a procedure that takes a user input and keeps asking for a user input until the input is “Hello”. If the input is not “Hello”, it should print “This is your n wrong try.” where n is the number of times they have put an input in. If they type “Hello”, the procedure should print “Success!”. Hint: != means does not equal

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19. Create a procedure to print stars and spaces in a roughly square pattern and have it take as input the number of stars on a side. Use a nested loop to do this.

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20. Write a procedure that takes an int argument and uses a while loop to create a right-triangle like shape out of *. The first row should have 1 star and the last should have n stars where n is the argument passed.

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